Metal fasteners, such as metal staples, are typically manufactured and sold in stick form, wherein the individual staple elements are placed into a close, contacting, abutting, generally elongated arrangement, and adapted to be inserted into an applicator. The metal staples in the stick form may vary in the quantity of staples, depending upon the particular use. Such individual staples have been secured together through the use of a thermoplastic adhesive material, such as a solvent-based nitrocellulose lacquer, which is coated onto the sides and top of the stick. The amount of the solvent-based thermoplastic adhesive material to be employed must be very carefully controlled, so that a relatively thin and uniform coating amount will be applied. If too much adhesive material is applied, then the adhesive material may tend to clog the applicator wherein the stick is employed, or if too little material is applied, then the individual staples are poorly secured in stick form prior to use.
Present adhesive materials employed constitute an organic solvent-based nitrocellular lacquer having a solids content of from about 20 to 35% which is applied to the staples in stick form, and the stick then heated to drive off the solvent. The speed of ccoating and applying such adhesive material is limited to the speed of the heating and driving off the solvents of the formulation. In production, the viscosity of the solvent-based formulation often varies, and additional solvents must be added to maintain an acceptable viscosity range, which solvent addition changes the amount of solids being applied to the stick, thereby varying the coating layer and adhesive amounts employed. Thus, the present technique of preparing metal fastener sticks and the metal fastener sticks so prepared are not wholly satisfactory, and have many disadvantages. It is understood that prior art attempts have been made to employ hot-melt adhesives as the adhesive material; however, such hot-melt adhesives have not shown the necessary viscosity characteristics which would permit the material to enter into the small fillet between the individual staples, particularly without building up an objectionably high solid adhesive content on top of the staples.
In general, metal staple sticks are prepared by one or two techniques, the first technique being passing a wire through a wire-drawing machine wherein individual staples are cut off and the point ends sharpened, with the individual staples packed onto a rail having a generally U-shape, one staple directly after another to keep the staples in a contacting arrangement. The solvent-based lacquer adhesive is then coated onto the top and onto the sides of the staples. Excess material is removed through a blade or a squeegeeing action, and, thereafter, the staples subjected to heat to drive off the solvent, such as through the electrical heating of the rail onto which the staples are formed, or by the employment of an oven.
A second technique is to employ a plurality of wires; for example, one or two hundred or more, which are placed side to side to form a flat band, and the band then coated on the bottom, top or both with the lacquer material. The adhesive-coated band is then force-dried and placed in rolls, and the rolls later are employed in a cutting and bending operation to form the individual staple sticks. Thus, in both processes, or in variations thereof, a solvent-based lacquer-type material is used, and in both processes such adhesive material requires careful control of viscosity and solids content and only limited production speed is possible, along with other disadvantages well known to the prior art.